1. Field of the Invention
The present invention relates to a display device, and more particularly, a liquid crystal display (LCD) device and a method of fabricating a liquid crystal display device.
2. Discussion of the Related Art
As the information age progresses, light weight, thin flat panel display (FPD) devices having low power consumption characteristics are being developed, and liquid crystal display (LCD) devices may be categorized as non-emissive display devices that are commonly used in notebook and desktop computers because of their high resolution, capability of displaying colored images, and high quality image display.
The LCD panel includes two substrates facing and spaced apart from each other, and a liquid crystal material in between. Liquid crystal molecules of the liquid crystal material have a dielectric constant and refractive index anisotropic characteristics due to their long, thin shape. In addition, two electric field generating electrodes are formed on each of the two substrates. Accordingly, an orientation alignment of the liquid crystal molecules may be controlled by supplying a voltage to the two electrodes, wherein transmittance of the LCD panel is changed according to polarization properties of the liquid crystal material.
FIG. 1 is a schematic perspective view of an LCD device according to the related art.
In FIG. 1, an LCD device 1 includes an upper substrate 10, a lower substrate 20 facing the upper substrate 10, and a liquid crystal layer 40 in between the upper and lower substrates 10 and 20. A color filter layer 14 is formed on the upper substrate 10, a black matrix 12 is formed on the color filter layer 14, and a common electrode 18 on the black matrix 12 and the color filter layer 14.
A gate line 22 and a data line 24 crossing the gate line 22 define a pixel region P and are formed on the lower substrate 20; a thin film transistor T is disposed near a crossing of the gate and data lines 22 and 24; and a pixel electrode 36 is connected to the thin film transistor T in the pixel region P.
The LCD device 1 may be referred as a LCD panel, and although not shown the LCD device 1 may further include upper and lower polarizers on outer surfaces of the upper and the lower substrates 10 and 20, respectively, a backlight unit under the lower substrate 20, and a top case and a bottom case supporting the LCD device 1.
FIG. 2 is a schematic cross-sectional view of an LCD device including upper and lower polarizers according to the related art.
In FIG. 2, an upper substrate 11 and a lower substrate 21 face each other, a common electrode 18 is formed on an inner surface of the upper substrate 11, and a pixel electrode 36 is formed on an inner surface of the lower substrate 21, and an upper polarizer 52 is disposed on an outer surface of the upper substrate 11 and a lower polarizer 50 is disposed on an outer surface of the lower substrate 21.
A liquid crystal layer 40 is in between the common electrode 18 and the pixel electrode 36.
Although not shown, an upper alignment layer is formed between the common electrode 18 and the liquid crystal layer 40, and a lower alignment layer is formed between the pixel electrode 36 and the liquid crystal layer 40. In other words, the liquid crystal layer contacts the upper and the lower alignment layers.
A desired gray level in the LCD device 60 may be obtained by controlling a transmittance due to birefringence of liquid crystal molecules of the liquid crystal layer 40. The birefringence is varies according to a vertical electric field between the common electrode 18. and the pixel electrode 36 when the electric field is applied to the liquid crystal layer 40.
However, to obtain the desired gray level, cell efficiency is not perfect because the birefringence decreases as viewing angle increases.
Furthermore, the LCD device 60 includes two polarizers, the upper and the lower polarizers 52 and 50, wherein the backlight unit light (not shown) may be shielded or reflected by the lower polarizer 50 closer to a backlight unit (not shown) than the upper polarizer 52.
Additionally, light leakage occurs due to surface reflections on the lower polarizer 50. Generally, the thickness of the polarizer is about 200 micrometers, and this feature is contrary to achieving a thin display.
In addition, the more the thickness of the polarizer is increased, the flexibility of the LCD device 60 is reduced due to the hardness of the polarizer.
Also, in order to compensate for the retardation ratio between a transmissive portion and a reflective portion in a reflective LCD device, a compensation plate should be added.
However, it is difficult to obtain a desired light transmission efficiency and a light and thin LCD device due to the addition of the compensation plate.